I recently installed CentOS 5.5 on an old Celeron-D with a TrendNet TEW-623PI Wireless N PCI adapter. It took some poking about on google and centos.org to figure out how to make it work with my access point. Here's the list of modifications I had to make. To give credit where credit is due, some of this is based on "http://wiki.centos.org/HowTos/Laptops/WpaSupplicant".
Install the ralink kernel module and firmware update (install the firmware first, since the kernel module depends on it)
[root@linux ~]# rpm -qa|grep rt28 rt2860-firmware-11-1.elrepo kmod-rt2860sta-2.1.2.0-2.el5.elrepo
Edit /etc/wpa_supplicant/wpa_supplicant
[root@linux ~]# cat /etc/wpa_supplicant/wpa_supplicant.conf ctrl_interface=/var/run/wpa_supplicant ctrl_interface_group=wheel network={ ssid="MYNETWORKSSID" key_mgmt=WPA-PSK psk="MYPASSKEY" }
Add the following to the end of /etc/sysconfig/network-scripts/ifup-wireless
if [ "$WPA" = "yes" -a -x /etc/init.d/wpa_supplicant ]; then /sbin/service wpa_supplicant start fi
Modified /etc/sysconfig/network-scripts/ifcfg-ra0
[root@linux ~]# cat /etc/sysconfig/network-scripts/ifcfg-ra0 # RaLink RT2800 802.11n PCI DEVICE=ra0 BOOTPROTO=static BROADCAST=192.168.10.255 IPADDR=192.168.10.141 NETMASK=255.255.255.0 NETWORK=192.168.10.0 ONBOOT=no HWADDR=##:##:##:##:##:## TYPE=Wireless WPA=yes DNS1=192.168.10.1 GATEWAY=192.168.10.1
Added one line to /etc/rc.local
/sbin/ifup ra0
Disabled the ra0 interface and wpa_supplicant service on boot
chkconfig wpa_supplicant off